Tweak ppoll() to include 1003.1-2024 visibility, take two

Note in the manpage that the 2024 edition finally added ppoll(), and
also add the appropriate declarations for the correct versions of
_POSIX_C_SOURCE (via __POSIX_VISIBLE).

Differential Revision:	https://reviews.freebsd.org/D48043

include/ssp/poll.h

@@ -42,7 +42,7 @@ __ssp_redirect_raw_impl(int, poll, poll,
 	return (__ssp_real(poll)(fds, nfds, timeout));
 }
 
-#if __BSD_VISIBLE
+#if __POSIX_VISIBLE >= 202405
 __ssp_redirect_raw_impl(int, ppoll, ppoll,
     (struct pollfd fds[], nfds_t nfds,
     const struct timespec *__restrict timeout,
@@ -53,7 +53,7 @@ __ssp_redirect_raw_impl(int, ppoll, ppoll,
 
 	return (__ssp_real(ppoll)(fds, nfds, timeout, newsigmask));
 }
-#endif	/* __BSD_VISIBLE */
+#endif	/* __POSIX_VISIBLE >= 202405 */
 __END_DECLS
 
 #endif /* __SSP_FORTIFY_LEVEL > 0 */